1. Field of the Invention
The present invention relates to a seat back of automotive seat, and in particular to a structure of the seat back which is easy to assemble.
2. Description of Prior Art
As is known in the art, assembly of a seat back of automotive seat involves attaching a padding over a seat back frame to provide a basic seat back unit and then enclosing such seat back unit with a three-dimensional trim cover assembly. The three-dimensional trim cover assembly is preformed by connecting a plurality of cover materials with one another, as by sewing, so as to assume a predetermined three-dimensional configuration that substantially conforms to outer contour of the basic seat back unit.
Hitherto, various attempts have been made to allow for easy covering the basic seat back unit with the foregoing three-dimensional trim cover assembly.
For example, the Japanese Laid-Open Patent Publication No. 2-177992 (hereinafter, “JP'992”) teaches a three-dimensional trim cover assembly having an opened region defined only in the lower bottom side thereof. In brief, according to the JP'992, at first, a whole of such three-dimensional trim cover assembly is turned over into a completely reversed state, so that entire reverse surfaces of the trim cover assembly are exposed outwardly, while entire outer surfaces of the same are disposed inside thereof. Then, a seat back frame and a foam padding are integrally secured to a backward side of such reversed trim cover assembly which corresponds to a backward side of a resulting seat back, and thereafter, a whole of the trim cover assembly is turned over and reversed relative to the backward side thereof, so that an entirety of the foam padding is covered with that particular trim cover assembly whose entire outer surfaces appear outwardly, In that manner, a finally finished seat back has the foam padding and seat back frame neatly disposed therewithin.
Also, known is a three-dimensional trim cover assembly having an local opened region defined in the backward side thereof for the purpose of allowing entry of seat back frame into the inside of trim cover assembly as well as for the purpose of allowing injection of a liquid foaming agent thereinto, as disclosed by the Japanese Laid-Open Patent Publication No. 2005-262628 (hereinafter, “JP'628”) for example. According to that JP'628, the three-dimensional trim cover assembly comprises: an opened area defined centrally in the backward surface thereof; and a cover element substantially conforming in shape to such opened area, wherein the cover element is at one side integral with the opened area and connectable with that particular opened area by means of slide fasteners. In assembly, a seat back frame is first inserted through the opened area (which is not covered with the cover element at this point) into the inside of the trim cover assembly, after which, the trim cover assembly is placed in a foaming die and subjected to known foaming process involving injection of a liquid foaming agent through that opened area into the trim cover assembly. Finally, after having removed a resulting seat back from the foaming die, the cover element is connected with the opened area by engagement of the fasteners to close the corresponding local backward side of the seat back.
However, with regard to the JP'992, it is quite difficult to properly reverse the trim cover assembly so that both foam pad and seat back frame are neatly covered with such reversed trim cover assembly, which may cause the possibility that both or either of the trim cover assembly and foam padding will be damaged or broken.
On the other hand, in the JP'628, the trim cover assembly remains a closed three-dimensional part in the upper end portion thereof as opposed to the opened area thereof, which requires some die elements for supporting and retaining such closed three-dimensional part. Further, it is technically difficult to cure the liquid foaming agent into a satisfied mass of foam padding in that particular closed three-dimensional part.
Obviously, for both of those prior arts, great difficulty has remained in terms of filling a foam padding satisfactorily in the trim cover assembly as well as of neatly attaching both of the foam padding and trim cover assembly to a seat back frame.